Okay i will throw this on this forum, someone tell me what a dummy load is supposed to do; check a transmitter output into a 50 ohm load, okay but that seems silly, pretty obvious, should work.I only use a dummy load to cut phase lines but what possible use beyond that can a dummy load be used for in this day of 50 ohm amps, tranceivers etc.Tuning up with a dumb load has no meaning, the antenna is where the energy needs to be monitored and very easy to accomplish with 5 watts for 2 seconds on that thing in your backyard so what does a dummy load do these days?Bob

obviously, crank out killer watts without putting them on the air. this is more useful than just boiling the oil if you are doing any repair work on the powered end. check spectrum, check to see if your tuner is shot, load up those new tubes and see if anything goes bang, see if you actually have power without jamming the band. if you can load the dummy, but not the antenna, that eliminates one possible failure point.

Nandu's hot plate has a resistance of 50 Ohms. This implies the DC resistance is 50 Ohms.

What is the impedance of the heating element at the frequencies the SB-200 is being tuned-up?

Specifically, how many Ohms impedance (Z) and at what phase angle? The reason I ask is because power transfer is also a concern. How inductive is the heating element?

How far does the RF coupled to the hot plate propagate? How well shielded is the hot plate at radio frequencies? What is the resonant frequency of the hot plate?

I had always thought using a well-shielded, reasonably noninductive (at the test frequency) dummy load was the best way to tune up a tube final PA without radiating much of a signal.

In the case of a solid-state transceiver either by itself or driving a solid-state amplifier, dissipating a test signal into a dummy load with an inline wattmeter to verify proper output in the event of poor system (including the antenna) performance is a helpful tool.

The Dummy Load, along with antenna switch, can and should be used for tuning up amplifiers and the older tube output radios, to avoid those long and annoying tuneups on the air by decreasing the amount of time needed to tune the thing once the antenna is connected.

I have a nice DX Engineering 8 position antenna switch. The heavy relaybox and coax is on the floor of the shack and the remote control box is on my operating table. It makes it easy and simple to change to a variety of antennas including the oil filled dummy load.

Copyright 2000-2018 eHam.net, LLC
eHam.net is a community web site for amateur (ham) radio operators around the world.
Contact the site with comments or questions.
WEBMASTER@EHAM.NETSite Privacy Statement